III International Conference

PP-II-39synthesized by deposition-precipitation of gold hydroxide on meso-macroporous mixed metaloxide support. The support and catalysts were characterized by XRD, SEM, HRTEM, N 2adsorption analysis and TPR measurements. No crystalline phase could be detected by XRDin the TZ support, indicating a homogeneous mixing of the Ti and Zr components in thesematerials. This suggests that the segregation did not occur, and meso-macrostructured TZwere formed with (Ti,Zr)-O 2 species, a real solid solution of TiO 2 and ZrO 2 , rather thandiscrete TiO 2 and ZrO 2 nanocrystallites. After calcination at 500 °C the bicrystalline phases oftetragonal ZrO 2 and anatase with low crystallinity were observed. The meso-macrostructurescan be retained after calcination, as revealed by SEM and TEM images. There are no visibledifferences in the X-ray patterns after deposition of gold. The absence of characteristic linesof gold at 2θ = 38.2 and 44.4° could be attributed to fine dispersion of gold nanoparticles onthe surface of TiZr. The gold particles with size below 4 nm are homogeneously dispersed onthe mixed metal oxide support. The pore sizes of the TZ were slightly enlarged aftercalcination. The BET surface areas and the pore volumes of the calcined TZ are larger thanthose of the calcined pure titania or zirconia, indicating the higher thermal stability of the TZmeso-macroporous materials. A significant effect of gold loading on the reducibility of theAu/TZ was found by H 2 –TPR. The catalytic behavior of the gold catalysts was evaluated inWGSR at a wide temperature range (140–300 °C) and at different space velocities andH 2 O/CO ratios. The influence of gold content and particle size on the catalytic performancewas investigated. The CO conversion of the new catalyst was compared with that related tothe gold catalysts supported on mesoporous ZrO 2 and TiO 2 . A high degree of synergisticinteraction between titania and zirconia was observed. Gold catalysts supported on the Au/TZexhibited significantly higher catalytic activity. New ZT support has been found to be ofmuch interest as potential supports of gold-based catalysts for WGS reaction.References1. V. Idakiev, T. Tabakova, Z.-Y. Yuan, B.-L. Su, Appl. Catal. A 270 (2004) 135.2. V. Idakiev, T. Tabakova, A. Naydenov, Z.-Y. Yuan, B.-L. Su, Appl. Catal. B 63 (2006) 178.3. Zhong-Yong Yuan, Tie-Zhen Ren, Aurélien Vantomme and Bao-Lian Su, Chem. Mater. 16(2004) 5096.235